Maroon and shaped like a boomerang, the liver is the second largest organ in the body (the skin always steals its glory). The reason it's so vital is that it serves as your body's border inspection station. Virtually every nutrient we consume, whether it has a valid passport or not, must pass through the liver so it can be transformed into a different biochemical form. That transformation is what allows the nutrient to be used, transported to a different location in the body or stored as an extra inch of blubbery goop on your thighs.

Structurally speaking, here's what you need to know about the liver. It's located just below the right rib cage in the upper right side of the abdomen, above the pancreas and the small intestine. Your liver does three main things: helps digest stuff, make proteins and gets rid of bad stuff. All the blood that has visited your small intestines flows through your portal vein into your liver, so almost all of the nutrients you eat have to pass through the gauntlet of the liver before passing to the heart for generalized distribution. Why almost? There's a little absorption in your mouth and under your tongue, but almost means 99 percent for the typical person. Your liver decides what gets kept out, what gets patted down and inspected and what's allowed in to be distributed throughout your body.

Within the organ, there's a network of bile ducts. Bile—if you remember—is the greenish liquid produced in the liver that helps break down fats. The liver also uses bile to clear bilirubin from the blood. Biliwhat, you say? Bilirubin—it's a substance that comes from the breakup of hemoglobin in dead red blood cells. An increased level of bilirubin results in jaundice—a yellowing of the skin and all mucous membranes that includes the eyeballs, where the yellowing is usually detected earliest and most easily—a sign of many liver diseases.